气体等离子体中太赫兹波辐射特性的理论研究

发布时间：2018-05-08 08:11

本文选题：气体等离子体 + 飞秒激光　；参考：《华中科技大学》2015年硕士论文

【摘要】：将飞秒激光聚焦在空气中形成气体等离子体,气体等离子体可以辐射出高强度、宽带宽的太赫兹波,是一种很有应用前景的太赫兹源,受到了人们的广泛关注。通常采用的激光是中心波长为800nm的飞秒激光以及它的倍频脉冲。本论文基于光电流模型,对气体等离子体辐射太赫兹波辐射的特性进行了理论研究,主要工作如下:(1)在一维情况下,使用光电流模型对太赫兹波辐射的基本特性进行了研究,分析了激光强度、基倍频脉冲相对相位差、电离饱和等因素对太赫兹波辐射的影响进行了研究。(2)研究了不同激光波长产生太赫兹波的区别,发现在一定波长范围内,太赫兹波强度随着使用激光波长的增大而增强。提出了使用800nm的飞秒激光以及其二分之一次谐波用于产生太赫兹波的方案,阐释了该方案的可行性以及实际意义。(3)结合实际中气体等离子体产生太赫兹波的方案,在二维情况下,对太赫兹波辐射的特性进行了研究,尤其是解释了椭圆偏振太赫兹波的产生原因。从理论上说明了太赫兹波椭圆偏振的原因并不完全是等离子体中各种效应,还与倍频晶体对激光偏振的影响有关。(4)研究了等离子体细丝的产生,结合等离子体的特性,分析了等离子体对激光脉冲传输的影响,包括光谱的展宽、色散带来的基倍频场相对相位差改变、交叉相位调制带来的偏振态的变化,在此基础上利用光电流模型推导出等离子体细丝对太赫兹波辐射的影响。
[Abstract]:The femtosecond laser is focused in the air to form a gas plasma. The gas plasma can radiate high intensity and broadband terahertz wave. It is a very promising terahertz source, which is widely concerned. The laser is a femtosecond laser with a central wavelength of 800nm and its frequency doubling pulse. This paper is based on this paper. The characteristics of the radiation of the terahertz wave radiation from gas plasma radiation are studied theoretically. The main work is as follows: (1) in one dimension, the basic characteristics of the terahertz wave radiation are studied by using the photocurrent model, and the factors such as the laser intensity, the relative phase difference of the basic frequency doubling pulse and the ionization saturation are analyzed. The effect of radiation is studied. (2) the difference of the terahertz wave generated by different laser wavelengths is studied. It is found that the intensity of the terahertz wave is enhanced with the increase of laser wavelength in a certain wavelength range. A scheme for using 800nm's femtosecond laser and its second harmonic generation to produce terahertz waves is proposed. The feasibility and practical significance. (3) combining the scheme of the terahertz wave produced by the gas plasma in the actual situation, the characteristics of the terahertz wave radiation are studied in the two-dimensional case, especially the cause of the elliptically polarized terahertz wave. It is theoretically explained that the reason for the ellipse polarization of the terahertz wave is not completely the plasma in the plasma. Various effects are also related to the effect of frequency doubling crystals on the polarization of laser. (4) the production of plasma filaments is studied and the effects of plasma on the laser pulse transmission are analyzed, including the broadening of the spectrum, the relative phase difference of the basic frequency doubling field caused by the dispersion and the change of the polarization state caused by the cross phase modulation. On this basis, the influence of plasma filament on terahertz radiation is deduced by using the photocurrent model.

【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O441.4

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